1. Field of the Invention:
This invention relates to a flying spot scanning system which modulates and reflects highly collimated light onto a scanned medium and, in particular, to an improvement for achieving half-tone imaging in the system.
2. Brief Description of the Prior Art:
Recent developments in the optical imaging of information have included the flying spot scanning system in which a collimated light beam is modulated in response to input video information and reflected by a mirror surface such as an oscillating galvanometer mirror or a multifaceted, rotating polygon. The reflecting surface is driven in a timed manner to sweep the reflected light beam in a scan across a focal plane imaging surface for an optical readout of the input information. The modulating facilities employed in these flying spot scanning systems modulate the intensity of the light beam in response to an analog video signal.
The flying spot scanning system has been applied to information reproduction systems such as xerography by positioning the focal plane readout surface adjacent the photoreceptive surface of a xerographic drum. The reflecting mirror or polygon is oscillated or rotated in a timed manner with the rotation of the xerographic drum to provide a series of continual scans of reflected and information-modulated light beams across the surface of the rotating xerographic drum. The limitation of the xerographic system, has heretofore precluded the reproduction of continuous tone images because of its inability to accurately and consistently produce continuous image tones other than black and white.
It is an object of this invention to provide a flying spot scanning system capable of creating half-tone images in a high contrast image reproducing system such as xerography.
Other objects will be apparent from the following description of the invention.